Hey all. Just landed at BOS on US shuttle flight 2154 from LGA. Was an e190. Several minutes before landing I noticed we started circling. After about 10 min the captain came on the pa and said that we were misconfigured for landing, that it wasn't an issue, and that they had finished running the checklists and we'd be landing shortly. Landing was fine, if not maybe a bit fast, and the usual equip was waiting. Before landing I noticed the slats were not extended and the flaps were at about 10%. I know we weren't in any danger, but I do have a couple questions just out of curiosity, as I fly 150k+ miles a year and have yet to have anything like this happen.

How common is this?
Is there redundancy that should be able to get the flaps in the right config?
If any, what's the real danger here?

Thanks all!

Quoting georgetown (Thread starter): How common is this?

I don't fly the 190, but within the context of irregular occurrences, flap issues are up there. I would guess they do happen daily but one or two out of several thousand flights each day isn't exactly common.

Quoting georgetown (Thread starter): Is there redundancy that should be able to get the flaps in the right config?

Transport category aircraft generally have redundant systems so if one fails you still have the ability to power various components (landing gear, flaps, etc) but there are a number of things that can happen to cause flap issues from a part physically breaking to hydraulic issues to electrical/system logic issues.

Quoting georgetown (Thread starter): If any, what's the real danger here?

Having to land with the flaps not fully extended generally raises the approach speed, which means you'll need a longer runway. For some airplanes you might run into tire speed limitations as well. Overall flap problems are fairly benign, with the emergency equipment being more procedural than anything. Unusual, sure, but nothing to start texting goodbyes over.

As I understand it, landing with no flaps or flaps not fully extended is not a huge issue. On the other hand, asymmetric flap/slat extension is quite gnarly. That's why flap systems tend to be designed to stop moving immediately if any asymmetry is detected.

Quoting georgetown (Thread starter): How common is this? Is there redundancy that should be able to get the flaps in the right config? If any, what's the real danger here?

It's not unheard of and in my career, I landed both a 727 and a 737 with abnormal flap configurations.

The posts above are correct, the configuration will result in a higher approach speed, so landing distance will increase. In some cases, a longer runway that originally planned may be needed.

As far as I know, the A380 is the only aircraft out there which is not allowed to land with the high lift system completely retracted (no slats and flaps).
All other types can land with no flaps and slats extended at all (you just need more speed, ergo more runway).

Quoting Trijetsonly (Reply 4): As far as I know, the A380 is the only aircraft out there which is not allowed to land with the high lift system completely retracted (no slats and flaps).

I suppose if they were unable to extend the slats and flaps, the choice would be to continue flying ad finitum!

Quoting georgetown (Thread starter): How common is this?

For the E190? Back in my B6 days the issue would come in waves just like the A320. To me the E190 is still fairly new, only been flying since late 2005 so it is still in its learning curve as the oldest frames are approaching 8 years old and packing on the cycles. There have been issues with sensors and various hardware that were addressed over time through Service Bulletins from Embraer and the various OEMs. But the issue does come around often enough to be addressed which I know sounds bad but is actually a good thing as a common issue over multiple aircraft and airlines is easier to investigate and find a solution for than a single occurrence. I'm thinking my buddy EMBQA down in BNA can go into a little more detail on this if he is watching  

Quoting georgetown (Thread starter): Is there redundancy that should be able to get the flaps in the right config?

Everything is built with redundancy factors, but making something completely error-proof would most likely make it completely uneconomical. In theory, part of the redundancy factor is just being able to continue flying the aircraft and landing it with the slats/flaps not configured completely.

Quoting georgetown (Thread starter): If any, what's the real danger here?

Not really. Whatever the fault was, the aircraft did what it was supposed to do when the fault appeared. Stop the slats/flaps from going into an un-even configuration and continue to a safe and successful landing even though it was a little faster than you are used to. Reverse thrust and carbon brakes will slow you down in plenty of time though.

Quoting georgetown (Thread starter): as I fly 150k+ miles a year and have yet to have anything like this happen

You are quite lucky. Even when I was with the airline I wouldn't fly nearly as much per year as that, but in my 8 1/2 years of being in the business and flying on my airline along with other ones I experienced flap issues, in-flight engine shut-downs, loss of steering, and a bunch of other minor things. If you fly as much as you do, you are going to get hit with some of the more interesting issues eventually LOL

Quoting B6JFKH81 (Reply 6): Quoting georgetown (Thread starter): as I fly 150k+ miles a year and have yet to have anything like this happen You are quite lucky. Even when I was with the airline I wouldn't fly nearly as much per year as that, but in my 8 1/2 years of being in the business and flying on my airline along with other ones I experienced flap issues, in-flight engine shut-downs, loss of steering, and a bunch of other minor things. If you fly as much as you do, you are going to get hit with some of the more interesting issues eventually LOL

georgetown may well have been on board with several such issues. However my guess is the flight crew doesn't get on the PA for every little thing or they'd have a lot of brown seats after the flights.

Thank you all very much for the responses here, very informative! I do feel lucky to fly as much as I do, and I figure these things will happen. It's funny, I was actually pretty calm about it in flight, and once we landed is when I became a touch unnerved. It's very true though, if the pilot hadn't said anything, it's very likely I would have just assumed atc made us circle a bit before an normal landing.

How common is this? As others have said, not very. It is, however, one of the more common issues. One of the major maneuvers that are demonstrated during a type rating exam is a no flap/no slat landing.

The EMBs are a bit more prone to it in my opinion because of the system design. Most larger aircraft have hydraulically actuated flaps and slaps. The 170/190 has electrically actuated flaps. There are two motors driving the slats and flaps. One of the major issues with this design is that the motors are put under great stress at speeds close to maximum speeds and it's not difficult to over speed the flaps. When I was flying the line I had two landings with the flaps failed in intermediate positions in three months. Our airline went through a rash of them and under the encouragement of Embraer started focusing on preventing flap over speed situations by extending the flaps at a slightly lower (and completely safe) speed.

As for the redundancy, yes, there are two motors. However there are also safeguards to prevent an asymmetric flap/slat extension and the general rule is: If something isn't right, don't screw with it. Having a flap/slat asymmetry is much more dangerous than a landing with reduced flap setting. For the 190 you were on, the worst case scenario requires only about 7000 feet of runway per the procedures established by the manufacturer.

Quoting Trijetsonly (Reply 4): As far as I know, the A380 is the only aircraft out there which is not allowed to land with the high lift system completely retracted (no slats and flaps).

Is that some limitation of the aircraft, or is it simply that there isn't a runway long enough? Could it land without flaps, say, on the lakebed at Edwards AFB?

Georgetown

...If any, what's the real danger here?...

The real danger, as Starlionblue was the first to point out, is when you have an asymmetric trailing edge flap configuration, that is, more flap on one wing than the other.

The flaps will now effectively be acting as ailerons and will exert a rolling moment on the aircraft. If this rolling moment exceeds the ability of the ailerons to oppose it, control of the aircraft may well be lost.

See here for an example of just such an accident, the aftermath of which I saw as a teenager.

That is why, again as others have said, commercial aircraft generally have protection devices that will halt any further flap movement as soon as any asymmetry is detected. If handled properly, flap asymmetry should not cause any undue problems, but if mis-handled, it can be exceedingly dangerous.

The other types of flap failures, where the flaps either fail to extend, or extend symmetrically but fail to extend fully, are generally more benign. Typically these are handled by the use of higher approach speeds and longer runways, and these failures are usually covered in depth on a simulator during conversion courses.

As an aside, as well as dealing with the failure itself and recalculating the landing distance required, a crew may well need some time to deal with other aircraft systems that might not now work, or may throw up a false or nuisance warning, because the flaps, or flap lever, are not in the normal position for landing.

Several aircraft systems can be tied up with the flap or flap lever position; GPWS, TCAS, Stick Shake, Wing Antice and Low Speed Aileron Unlock are just some of the systems that may be affected on some aircraft.

I've had three Split Flap landings and one Asymmetric Flap landing on the B747 in my career, a problem I solved by bidding on to an aircraft that didn't have any flaps!

Best Regards

Bellerophon

Quoting Bellerophon (Reply 11): I've had three Split Flap landings and one Asymmetric Flap landing on the B747 in my career, a problem I solved by bidding on to an aircraft that didn't have any flaps!

This one?

Quoting Bellerophon (Reply 11): That is why, again as others have said, commercial aircraft generally have protection devices that will halt any further flap movement as soon as any asymmetry is detected. If handled properly, flap asymmetry should not cause any undue problems, but if mis-handled, it can be exceedingly dangerous.

When assymetry is detected on the types I have worked on it will stop all flap movement until the flap control unit has been reset by maintenance back on ground.

Another flap problem which is particular to the CRJ-100/200 is flaps not extending due to frozen actuators. Water would enter the actuator if it hadn't been properly sealed and freeze when the aircraft reached cruising altitude, the result being a flaps up landing. It happened a lot, especially in the winter, until a few years where they finally managed to come up with a waterproof flap actuator.

/Lars

Quoting larshjort (Reply 12): Another flap problem which is particular to the CRJ-100/200 is flaps not extending due to frozen actuators. Water would enter the actuator if it hadn't been properly sealed and freeze when the aircraft reached cruising altitude, the result being a flaps up landing. It happened a lot, especially in the winter, until a few years where they finally managed to come up with a waterproof flap actuator.

That was so annoying before Bombardier started figuring out how to fix it. No flap landings happened so often that the air traffic controllers at our hubs didn't even bother asking if we needed emergency vehicles standing by, as they already knew the answer was 'no'. On the plus side, we became quite skilled at no flap landings.  

larshjort

What, single engine, no toilet, and no flight engineer? Not for me!  

But mine did have a tailwheel!  

Best Regards

Bellerophon

Quoting cornutt (Reply 10): Is that some limitation of the aircraft, or is it simply that there isn't a runway long enough? Could it land without flaps, say, on the lakebed at Edwards AFB?

AFAIK this was only possible due to the very low calculated risk of a high-lift-system failure.
I don't know what's the reason for the missing clearance for a flapless landing but I guess the the high tire speed could be it.
That's the only link that I've found on google's first page of search results:
http://www.aviationtoday.com/regions...-A380-Special-Conditions_2441.html

Quoting Bellerophon (Reply 14): But mine did have a tailwheel!

And reheat (afterburners to us wayward colonies) you Ba$tard..  

Dan in Jupiter

Quoting Bellerophon (Reply 11): Split Flap landings

Quoting Bellerophon (Reply 11): Asymmetric Flap landing

Hi Bellerophon - what's the difference between the two situations you listed here? I'm not familiar with "split flap" landings.

Thanks.

Hi vikkyvik

... I'm not familiar with "split flap" landings...

It is a problem that can occur on those aircraft where the trailing edge flaps on each wing consist of more than one section of flap.

The B747 is a good example of this, as shown in this photo by Sam Chui


View Large View Medium

Photo © Sam Chui

with each wing having two sections of flap, designated inboard and outboard.

Split Flaps refers to the situation where either both inboard or both outboard flaps respond normally to flap lever selection but the other pair either fail to move at all, or move symmetrically but stop short of the selected position.

For example, let us say that we are on approach, reducing speed, with Flap 5 set.

On selecting Flap 10, we observe that the Inboard flaps move to Flap 10 but the Outboard flaps remain at Flap 5. This is called a Split Flap failure.

The crucial difference here is that, whilst we have a problem, there is no rolling moment being generated by the flaps, because the position the failed flap sections have stopped at is the same on both wings.

Now permit me to leave aside how or why Split Flaps might occur - because that is a substantial part of a B747-100/200 conversion course - and to generalise considerably for the sake of brevity,

In this Split Flap failure, even if the Outboard flaps would not lower past Flap 5, then after following the Non-Normal checklist it would be safe to continue to lower the Inboard flaps to Flap 30, because that would not generate any rolling moment.

We would still have to consider an increased approach speed, using a longer runway, a different approach attitude and a whole host of other items before commencing an approach, but at least we could still continue to utilise the pair of flaps that were still operating normally to give us a bit more lift - and thus a slower approach speed - on approach.

Contrast this with an Asymmetric Flap failure.

If we go back to the same point on approach where we selected Flap 10, this time we observe that the Inboards flaps move to Flap 10 but the left Outboard flap moves only to about Flap “6” whilst the right Outboard flap moves to about Flap “8” before the asymmetry protection system detects the fault, locks the Inboard flaps and throws up a Master Warning.

This is an Asymmetric Flap failure. Something is badly wrong with the left Outboard flap, and - if it were possible - and if we were foolish enough to continue to lower the flaps further, the increasing asymmetry between the left and right outboard flaps would carry the very real danger of inducing an uncontrollable rolling moment to the left.

The procedure for dealing with asymmetric flaps - in my experience fairly universal amongst major operators - is leave them where they are, follow the checklist and land. Your engineers can then trouble shoot the fault safely on the ground and tell you exactly what went wrong a couple of days later.

Engineers like explaining things to pilots! (Generally only once though)   

Best Regards

Bellerophon

[Edited 2013-11-18 16:46:56]

Quoting EGGD (Reply 5): I suppose if they were unable to extend the slats and flaps, the choice would be to continue flying ad finitum!

Yes. "Flaps Malfunction Endangers A380" "Pilots make safe landing" "Obviously, pilots arrested for this outrage"

Quoting Bellerophon (Reply 18):

Thank you very much for the detailed explanation!